1. Field
The present disclosure relates to a new method and system for the sequencing of weld beads. In one embodiment, the present disclosure relates to utilizing a numerical analysis to determine a weld bead sequence that may reduce distortion and/or stress caused by the welding process.
2. General Background
When selecting a metal for a particular application, the demands of the application may require physical characteristics which cannot be met by a single composition. Some alloys, for example, may provide suitable characteristics in terms of mechanical properties but lack the necessary physical characteristics such as resistance to corrosion or erosion.
In such an instance, one solution is typically found in overlaying a metal having the requisite structural characteristics with an alloy or another metal having the desired physical characteristics by welding and other similar processes.
Welding has both positive and negative effects on the properties of base metals being joined and the previously deposited metal. In many welding processes, weld beads are placed at specific locations in or at the surface of the weld for the purpose of affecting the metallurgical properties of the heat-affected zone or previously deposited weld metal.
The application of a layer of weld beads to cover a surface, may cause residual stress as a result of the welding process. The heat input causes melting and re-solidification of the applied metal. As a result, residual stresses may result in physical distortion of the surface or the geometry of the component.
Typically, allowances are made in the dimensions of the component to allow for dimensional changes after the application of the overlay. However, this is an inexact science and dimensional changes have been very difficult to predict or calculate except in cases of very regular parts.
In other cases, components may be constructed oversized and following application of overlay, cut to specified size.
Distortion of components can sometimes be resolved with mechanical straightening and stress relieving heat treatments. However, this approach may only be effective in resolving some simple dimensional distortions such as flatness. In most cases there are no practical methods of returning a large, complex component, for example, a boiler tube panel, to its original size and specification.
Efforts to date have focused on minimizing the effects of weld overlay application. For example, various methods have been utilized to try and reduce the stress of applying a weld overlay on boiler tube panels. This includes running water through the tubes during the weld overlay process to minimize the heat buildup and accelerate the cooling of the weld overlay. Further, efforts have also been made to precisely manage the input parameters of the weld process to minimize the heat input.